It turns out that the pulsations is caused by color assimilation, and the wiggling happens due to “ambiguous figure-ground segregation” (whatever this means), as Peter van der Helm discusses in his paper (2007).

So what does all of this have to do with our latest optical illusion, you ask? Not much except visual similarity, I guess. I just thought it would be cool to mention ninjas and shurikens in the paragraph above. Ok, now let me explain how the illusion works – If you concentrate on the central dot in the animation below, after seeing the first frame consisting of two overlapped colored objects, you get the impression next two frames are showcasing isolated objects filled with appropriate fluorescent color! In reality, all frames except first lack color, and what you perceive as color afterwards is just an afterimage burnt in your retina! Don’t worry though, it only lasts couple of seconds…

Concentrate on the black central dot, and see the colors magically appear!

Color vision deficient people have a tendency to better night vision and, in some situations, they can perceive variations in luminosity that color-sighted people could not. It might also be worth mentioning how U.S. Army discovered that color blind people could spot “camouflage” colors that fooled those with normal color vision!

Regular Color Blindness Test no.1

Now let’s see if you are able to find a circle, star, and/or square in this Demonstration Card below. In reality, everyone should be able to see a circle, star, and square as this is a demonstration piece only.

Regular Color Blindness Test no.2

Let’s see how the previous, “normal” tests worked like. Try and find a circle, star, and/or square in 3 seconds or less in this picture below. While the colorblind individuals should only see the yellow square. Color normal individuals should see the yellow square and a “faint” brown circle.

Regular Color Blindness Test no.3

The question is same -are you able to find a circle, star, and/or square in 3 seconds or less in this picture below? Just the opposite from previous test, colorblind individuals should now see the yellow circle, while color normal individuals should see the yellow circle and a “faint” brown square.

Hue is one of the main properties of a color, defined technically as “the degree to which a stimulus can be described as similar to or different from stimuli that are described as red, green, blue, and yellow” (those beeing the unique hues). The other main correlatives of color appearance are colorfulness, chroma, saturation, lightness, and brightness.

In painting color theory, a hue refers to a pure color—one without tint or shade (added white or black pigment, respectively). A hue is also an element of the color wheel. Hues are first processed in the brain in areas in the extended V4 called globs.

Now let’s try and explain the science behind this: Troxler’s Fading or Troxler’s Effect is a phenomenon of visual perception you have just experienced moments ago. When one fixates a particular point, after about 20 seconds or so, a stimulus away from the fixation point (in peripheral vision) will fade away and disappear. The effect is enhanced if the stimulus is small, of low contrast, or blurred. It works best the further the stimulus is away from the fixation point.

Troxler’s fading was first discovered by Ignaz Paul Vital Troxler, back in 1804. It is part of the general principle in sensory systems that an unvarying stimulus soon disappears from our awareness. Here’s a fun experiment you can try yourself: place a small piece of paper on the inside of your forearm. You can feel it for a few seconds, but then the sensation is no longer present. This is because the tactile neurons have adapted. Now, if you jiggle your arm up and down, giving varying stimulation, you will continue to feel the paper until it falls off! Similar fading can be seen of a fixated stimulus when its retinal image is made stationary on the retina, a stabilized retinal image. One can induce an afterimage, usually by an intense, brief flash, such as when one is photographed using a photographic flash.

This causes an image to be bleached onto the retina by the strong adaptation of the rods and cones. In all these cases, the stimulus fades away after a short time and disappears. Troxler’s fading can occur without any extraordinary stabilization of the retinal image in peripheral vision because the neurons in the visual system beyond the rods and cones have large receptive fields. This means that the small, involuntary eye movements made when fixating something fail to move the stimulus onto a new cell’s receptive field, giving unvarying stimulation. One of the more famous examples we covered in the past was Lilac Chaser. Be sure to check Disappearing Effect category for many more examples of Troxler’s Effect!

For today’s illusion, just stare at the nose of this gorgeous clown below. Try not to blink nor move your eyes for 30 seconds. Then quickly more your eyes over the white surface (ordinary wall will do fine, or use the provided white space below), and start blinking obsessively! What do you see? Hope you liked this afterimage as much as I did! Thanks goes to Mathieu and Mauro for sending this!

It was pretty popular back in the “old days”, as you could easily make your own unique spinner using nothing but piece of cardboard, a pencil and a toothpick! So what is so special about it? In 1894, toymaker Mr. C.E. Benham discovered that a spinning disk with a particular pattern of black and white marks could cause people to see colors! Mr. Benham called his disk an Artificial Spectrum Top and sold it through “Messrs, Newton and Co.”

Benham’s Top (or Benham’s Disk) has puzzled scientists for over 100 years. Let’s see if the spinning black and white disk can fool you into seeing some colors?! Do you think you can understand why is this happening? At some point, you should also be able to see a radiation warning sign inside the spinner!

Youtuber who goes under the name of brusspup noticed how this illusion has been around for a long time but always in the form of an image. His goal was to take it away from a flat piece of paper and turn it into a real, life-sized illusion that people could interact with. Obviously, brusspup has succeeded. He even included a scaled-down template for us to download and play with (file courtesy – brusspup).

Here’s how the author explained the effect and what he has done to achieve it:

The illusion works because of the “shadow” that falls on the checkerboard. Lets think of the square that the shadow falls on. Now picture that the shadow doesn’t exist: you would see a light colored square surrounded by the dark colored squares. But when the shadow falls on top of that light colored square, the shadow causes the shade to become darker but it also causes the surrounding darker squares to become darker. So within the shadow region the brightness and darkness of the squares are still relative to one another. But they are no longer relative to the squares that lie outside of the shadow.

So if you were able to pick up the middle square and move it to one of the outside dark squares, they would be 2 different shades, But the trick is ..that when you move the square you are moving it WITH the shadow still printed on the square. So now you’ve moved it out of its relative area, outside of the shadow region (but with the shadow still printed on the square) ..to the area where it’s the same shade as the “dark” square.

Try and focus on the right (sharp) part of the photo on your right. The photo shows something that resembles two lighthouses, but I can assure you it would’ve worked even if the motive was carrots. After some time the image has changed, and the right lighthouse turns blurry. You’ll get the impression the left lighthouse is now sharper than the right one. In reality the new image contains two identically blurred lighthouses. Not sure if I managed to explain this well enough, but I can assure you this illusion deserves some extra attention!

Created by Erica Dixon, Arthur Shapiro and Kai Hamburger “Grouping by Contrast” presents luminance levels of four disks modulating in time. The top two disks become white when the bottom two disks become black (and viceversa), but when they are placed against a split background, the disks group together along the diagonals giving the illusion their modulation is out of sync. This grouping pattern follows the contrasts of the disks relative to their backgrounds. You are welcome to test this theory by playing with the interactive button below.